This invention relates to an apparatus for cutting and stirring curd. Such apparatuses are known from practice and comprise a tank in which a rotatable shaft is situated which carries cutting frames extending radially from the shaft, which cutting frames are mounted on the shaft in staggered relation. The cutting frames each comprise two spaced-apart parallel frame girders, which are mounted by one end on the rotatable shaft and whose other end extends to a point near the wall of the tank. The tank can be disposed horizontally or vertically, the rotatable shaft then being likewise horizontal or vertical.
Arranged between the frame girders is a lattice of longitudinal and transverse knives. The transverse knives extend transversely to the frame girders and are welded to them. The longitudinal knives extend parallel to the frame girders and are mounted on the transverse knives by welding.
Such an apparatus is, for instance, the curd vat marketed by Tetra Pak Tebel under the name of OST4. Such an apparatus is also described, for instance, in U.S. Pat. No. 4,108,058. A variant with two horizontal shafts in a horizontal oval tank is described in U.S. Pat. No. 4,989,504.
All known apparatuses are arranged for stirring and cutting curd which has formed in the tank in that the tank has been filled with milk to which starter and rennet have been added. To that end, the central shaft is driven for rotation, so that the cutting frames move through the curd formed. The cutting frames are usually designed such that the knives and the frame girders form a cutting edge along one edge and are blunt and rounded off along the other edge. Accordingly, rotation of the central shaft(s) in one direction substantially yields a cutting action, while rotation in the other direction substantially yields a stirring action.
A problem occurring in the known apparatuses is that on the wall of the tank plaques of curd may form, which are not carried along by the knives of the cutting frames. Such plaques often come off the wall in a later stage, for instance during stirring, subsequent to cutting. If the plaques come off in such a late stage, comminution of the plaques takes place too late, which has an adverse effect on the homogeneity of the cheese to be produced, since the point of cutting the curd is to promote moisture egress. In the event of plaques or chunks undergoing a cutting operation later than the rest of the curd, moisture egress sustains a delay, which has a direct influence of the homogeneity of the cheese to be produced.
The object of the invention is to obviate the problem outlined and generally to make available a reliably and effectively working apparatus for cutting and stirring curd, which enables the production of a qualitatively superior-grade cheese.
According to the invention, an apparatus for cutting and stirring curd, comprising a curd vat with a shaft drivable for rotation, which shaft comprises a number of cutting frames extending radially from the shaft and having a number of strip-shaped transverse knives and longitudinal knives, the longitudinal knives each having an inner end situated near the shaft and an outer end situated near the wall of the curd vat is characterized in that at least a number of longitudinal knives of at least one of the cutting frames are provided, at the outer end situated near the wall of the curd vat, with a knife end section which has at least one portion extending transversely to the longitudinal direction of the longitudinal knives.